When it comes to contactors, they have the advantages of fast action, safe and convenient operation, easy remote control, and protection against undervoltage and zero voltage. They are widely used in electric motors, welding machines, small generators, and machine tool control. Therefore, it is necessary to master the ability to quickly resolve faults. In this article, we will share the most common methods for resolving faults in contactors?

1、 Contact system malfunction

       1. Contact overheating burns

       This problem often occurs in frequent starting or long-term operation of motor control, mainly due to the contactor starting too frequently or insufficient contact capacity, three-phase contacts not synchronously contacting, impurities or unevenness on the contact surface, uneven wear on the contact surface, and other reasons.

      Solution: If the contact is overheated and burned, it needs to be smoothed or the contactor contact needs to be replaced (if economically feasible, the contactor can be directly replaced) before continuing to use. Otherwise, it is easy to cause contact adhesion or overheating and melting, resulting in short circuit or phase loss problems in the main circuit. If the capacity of the contactor is insufficient and needs to be replaced with a larger and more high-capacity contactor.

       2. Contact welding

       The high position generated by severe arcing can cause the contact surfaces of the moving and stationary contacts to melt and weld together, making it impossible to break. The phenomenon of contact fusion welding is usually caused by factors such as insufficient contact capacity, damaged contact spring, reduced initial pressure, and short circuit on the load side.

       Solution: Replace severely damaged contacts or directly replace the contactor

       1) The iron core of the contactor cannot be attracted

       The working coil voltage of the contactor is too low, the circuit is incorrect, the coil is broken or burned, the mechanical part of the armature is not flexible or the moving contact is stuck, the auxiliary contact is loose or stuck in the slot, etc

        Specific processing method:

        If the voltage is too low, the contactor will frequently open and close. It is necessary to check the control power supply or control circuit and adjust the voltage to reach the normal value;

        Firstly, check the voltage at both ends of the contactor coil. If there is no voltage, check the control circuit or replace damaged electrical components;

        Replace the coil or contactor, and if it is an external bow, external faults need to be eliminated;

        Replace the coil or contactor, and if it is caused by external factors, external faults need to be eliminated; Repair mechanical faults of contactors, remove rust, and add some lubricating oil at the mechanical action points; It is necessary to check if the auxiliary contacts are loose to ensure proper installation. If the movable card slot is worn, replace the auxiliary contacts;

       2) The contactor iron core releases slowly or cannot be released

       Residual magnetism or dirt on the end face of the iron core causes the moving and stationary iron cores to adhere together. The non-magnetic gasket of the DC electrical appliance is damaged, causing faults such as a decrease in the minimum air gap after the armature is closed. Solution: If there is dirt on the end face of the iron core, it should be cleaned with gasoline. If the non-magnetic gasket of the DC electromagnetic is damaged, replace the gasket or contactor directly.

       3) The contactor wire is tightly fixed, overheated or smoking, and burned

       The reasons are coil turn to turn short circuit, insulation aging, and power supply voltage lower or higher than the working voltage of the coil. Solution: If there is a short circuit between the turns of the coil or insulation aging, the coil or contactor should be replaced. If the working voltage of the coil does not match the power supply, the coil with a working voltage that matches the power supply voltage should be replaced.

       4) Excessive noise

       It is possible that the short-circuit ring of the AC contactor is broken or the end faces of the moving and stationary iron cores are uneven, skewed, or dirty, which may cause the issue. Solution: Remove the coil and flatten or grind the iron core pole surface, or clean the oil stains with gasoline. If there is a short circuit or breakage, replace the iron filings or contactors. If the iron core is skewed, it should be corrected or tightened.

       The above are the common causes and solutions of contactor faults for your reference.